The instant invention relates to electrical terminals and more particularly to a terminal which can be effectively utilized for both hermetic and nonhermetic applications and which is operative for interrupting the flow of electrical current therethrough when it is operated under high temperature conditions such as caused by electrical overloads.
A number of different types of terminals have been heretofore available for use in transmitting electrical currents through the walls of both hermetic and nonhermetic housings containing electrical apparatus and/or circuitry. In this regard, hermetic terminals of this general type are disclosed and illustrated in the U.S. patents to DODENHOFF, U.S. Pat. Nos. 3,988,053, MILLER, 4,252,394, and BOWSKY, 4,296,275, which represent the closest prior art to the instant invention of which the applicants are aware. Hermetic terminals of the general type disclosed in these patents have been primarily utilized for passing electrical currents through the walls of hermetically sealed compressor housings, such as those which contain pressurized gases and/or liquids, and they have been generally mounted in openings in the walls of the housings for providing hermetic electrical communication between electrically conductive elements on the interiors and the exteriors of the housings. In any event, it has been found that since terminals of this type have frequently been used for passing currents through housings which contain pressurized gases, such as Freon, as well as other pressurized gases and/or liquids, it is important that they be constructed so that they maintain their structural integrity under all conditions.
While a number of the heretofore available electrical terminals of this general type have been found to be effective under normal operating conditions for providing electrical communication between the exteriors and interiors of housings, they have sometimes been less than entirely effective when they have been operated under high temperature conditions, such as caused by electrical overloads. In this regard, most of the heretofore available hermetic terminals of this type have comprised a cup-shaped body having one or more apertures therethrough, one or more elongated terminal pins which extend through the apertures, and one or more glass seal elements which electrically insulate and seal between the terminal pins and the body in the areas of the apertures. It has been found that in remote instances, such as under high temperature electrical overload conditions, one or more of the pins of a hermetic terminal of this type can become heated to the extent that the adjacent glass seal elements are melted. Although the chances of this occurring are extremely remote, when it does occur, the integrity of the seal provided by the terminal can be lost and gas and/or liquid contained in the interior of the housing can leak through the apertures in the terminal. Further, it has also been found that if the flow of electrical current through a terminal of this type is not somehow interrupted during electrical overload conditions, substantial damage can occur to the electrical apparatus and/or circuitry contained in the housing to which the terminal is connected.
The instant invention provides an improved terminal construction which can be effectively utilized for hermetic applications, such as for refrigeration compressor housings, and also for nonhermetic applications, and which has substantially improved reliability for maintaining its structural integrity under high temperature overload conditions. In this regard, the terminal construction of the instant invention comprises a body having an end wall with an aperture therethrough, a pin made of an electrically conductive material extending through the aperture in the end wall and a distance therebeyond on each side thereof, and an electrically insulating seal bonding the pin to the end wall. The pin has an inner end which is disposed on the inner side of the body and an outer end which is disposed on the outer side of the body and it comprises first and second pin sections and a fusible section which interconnects the two pin sections in substantially aligned relation at a point in the extent of the pin which is not bonded to the seal. The fusible section is made of a material having a melting point which is sufficiently less than the softening point of the material from which the seal is constructed so that when the pin is heated, the fusible section melts to permit the two pin sections to separate before integrity of the seal is lost. The terminal is preferably constructed so that the first pin section extends through the aperture, so that the seal is bonded to the first pin section and so that the fusible section is disposed between the seal and the inner end of the pin. Further, preferably the seal is made of glass and at least the first pin section is constructed of stainless steel so that an enhanced bond is provided between the pin and the seal. Preferably the second pin section is formed with a socket element on the end thereof which is connected to the fusible section and the fusible section and the adjacent end of the first pin section are received in the socket element. In addition, a substantially radially extending flange is preferably formed on the second pin section adjacent the end of the socket element and an electrically insulative disc is received on the pin between the flange and the body. In this regard, it has been found that when the terminal of the instant invention is constructed in this manner, the socket element and the flange facilitate the assembly of the two pin sections by maintaining them in substantially aligned relation while they are secured together with the fusible section.
As a result of the above features, the terminal construction of the instant invention effectively solves the problem of maintaining the integrity of the seal provided by a hermetic terminal, even when it is operated under high temperature conditions, such as caused by electrical overloads. In this connection, it has been found that in most cases, the first and second pin sections of the terminal of the instant invention effectively separate well before the temperature of the adjacent seal of the terminal reaches its softening point. As a result, the flow of current through the terminal is normally interrupted before the integrity of the seal provided by the terminal is lost and, in most instances, before electrically operated equipment connected to the terminal is destroyed.
Accordingly, it is a primary object of the instant invention to provide a terminal construction which can be utilized for both hermetic and nonhermetic applications and which is operative for interrupting the flow of current therethrough when it is operated under high temperature electrical overload conditions.
Another object of the instant invention is to provide a hermetic terminal, wherein the integrity of the seal provided by the terminal is normally maintained even when it is operated under high temperature electrical overload conditions.
A still further object of the instant invention is to provide a hermetic terminal comprising a body, a terminal pin having first and second pin sections which are interconnected in substantially aligned relation by a fusible section and a seal element which seals between the pin and the body, wherein the fusible section is made of a material having a melting point which is substantially less than the melting point of the seal element.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.